In an electric dust collecting-type air cleaning machine or an electrophotography copying machine employing an electrification method by corona discharge, since corona discharge is performed in the air in the machine, a large amount of ozone is generated in the machine. Since this ozone is a gas having a very strong odor and high oxidativeness and, for example, only due to the presence of a concentration of 0.1 ppm in the air, causes the physiological action such as breath shortness, dizziness, nausea and headache, leakage of such the ozone to the outside of an each instrument must be avoided.
In order to overcome such problems, various filters decomposing ozone are proposed. There are a variety of forms and, when an attention is paid to an ozone-decomposing agent, there are following:
First, an ozone-decomposing agent in which a pore volume of activated carbon is controlled has been disclosed (e.g. see Patent Document 1).
However, there is a problem that, even when a pore volume of activated carbon is controlled, since decomposition is a carbon losing reaction, a deterioration rate of carbon becomes great with time, and a high efficacy can not be maintained over a long period of time.
Further, an ozone-decomposing agent in which α-FeOOH and 5Fe2O3.H2O are carried on a surface of activated carbon has been disclosed (e.g. see Patent Document 2).
Such procedure is an activated carbon-dependent decomposition reaction, and can maintain a higher efficacy than that of single activated carbon, but there is also a problem that a deterioration rate becomes great with time and a high efficacy can not be maintained over a long period of time.
On the other hand, various ozone decomposing agents derived from an iron-copper composite oxide have been disclosed (e.g. see Patent Documents 3 and 4).
However, since a composite compound of iron oxide and copper oxide is insufficient in the ozone-decomposing performance capability, the ozone-decomposing performance capability is improved by using a noble metal jointly, and a catalyst therefore becomes extremely expensive, resulting in difficulty in wide industrial utilization.                Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 56-168824        Patent Document 2: JP-A No. 2002-233718        Patent Document 3: JP-A No. 62-201648        Patent Document 4: JP-A No. 02-187148        